1. Field of the Invention
The present invention relates to a method for manipulating nanoparticles, and more specifically the present invention relates to a method for using radiation to directly assemble and fuse nanoparticles into larger scale structures.
2. Background of the Invention
In microelectronics, device performance is strongly related to the microstructure and patterns of electrically-conductive channels. In the field of organic electronics, for example, the creation of high-conductivity and high-resolution microcircuits is a major challenge. Typical conductivities of soft organic materials are ˜10−6 S/cm, limiting their practical implementation in electronics. On the other hand, conventional electronics is based on solid inorganic materials with very high conductivities (˜103-105 S/cm) but with limited mechanical robustness and flexibility.
The controlled synthesis or fabrication of complex materials and devices from nanoparticles (NPs) is a major goal of modern nanoscience. NP assembly is carried out either with top-down or bottom-up approaches. Top-down approaches involve depositing, patterning, and etching material layers. These invasive procedures typically rely on control of damage, and as the structures approach smaller length scales, the increased number of manufacturing defects makes device operation problematic.
Of bottom-up techniques, printing is the most widespread method. However, printing cannot fabricate effectively at small length scales without special surface templating. Other bottom-up methods include trapping individual NPs and nanowires using applied electromagnetic fields, or ligands. Post-synthesis assembly techniques for integration into high-density device assemblies include electric and magnetic-field-assisted alignment, optical and optoelectronic tweezers, micro-fluidic flow channels and micro contact printing. These methods involve multiple steps and can be limited by low deposition rates, lack of permanent bonding mechanism, and low electrical conductivity of the resulting microcircuits.
However, controlled synthesis of “user-designed” architectures from colloidal NPs that extend over microscopic and mesoscopic length scales is challenging due to a lack of understanding of the growth mechanisms and parameters defining the final architecture. Other challenges are the stability of the assembled NPs and the fact that surfactant layers might limit the durability of mesoscopic aggregations.
Lithographic techniques are currently used for nano-patterning. Expensive equipment and processes are used to create the patterns. The techniques are limited in the material choices, size, scale and patterning speed.
Other processes exist for manipulating large particles (i.e., between 2 and 15 microns in size) of compounds. These processes produce nanowires solely of the compounds, which are bound together by van der Waal's forces. The structures which result from such large particle manipulation are not porous and not stable. Also, the use of large particles prevents the creation of patterns and fine detail structure.
A need exists in the art for a process for providing controlled irreversible assembly of stable NP structures with intricate shapes and arbitrary sizes. The process should allow for fine-tuning of the forces which drive the assembly so as to enhance surface area and porosity of the resulting structures. Also, the process should allow for real time fabrication and manipulation of resulting assemblies, all using low power, and therefore less hazardous, energy sources.